This invention relates to butterfly valves, and more particularly to a valve of improved construction and operation.
Butterfly valves have several problems inherent in their design. Most significant is the adverse generation of particulate matter resulting from the outside diameter of the valve disk scrubbing against the valve liner in order to effect a seal. Additionally, this type of sealing is quite prone to leaking. Still further, replacement of the valve liner requires substantially complete disassembly of the valve. A typical butterfly valve is disclosed in U.S. Pat. No. 3,521,857.
Attempts to improve the effectiveness of butterfly valves have included the association therewith of the structure and function of poppet valves. Some of these hybrid butterfly valves have improved sealing effectiveness, but have not overcome the adverse generation of particulates. Some interfere with flow of material through the valve, while others allow only one-way flow. All involve complex and costly constructions which are not suitable for vacuum and sterile applications. Typical of these hybrid butterfly valves are those disclosed in U.S. Pat. Nos. 5,118,078; 4,921,212; 4,817,916; 3,065,950; and 2,673,061.